"When they come close to the Sun, this ice melts - solar wind blows this material out into space, so you get a tail of matter coming off the comet, " explains O'Brien.
When asked why he had only brought the matter to the attention of the Tribunal this morning, Mr O'Toole said he had looked up the terms of reference in Garda headquarters after hearing the evidence last September of Gerry Collins, the Republic's justice minister at the time of the murders.